Tube rating question

[infrared72]

I'm looking to purchase an extra set of 6v6's and EL84's for my Rebel 30. Can someone enlighten me as to the whole Low, Medium, and High rating on tubes? I'm looking at Groove Tubes and Electro Harmonix tubes on musician's friend just to get an idea of cost and such. The Groove tubes have a Low/Medium/High Rating, Duet or Quartet. I get the part of buying 2 or 4 at a time depending on your amp - what I don't get is the Low/Med/Hi. What's that all about?

Electro Harmonix uses a Soft/Med/Hard rating on their EL84 duet or quartet of tubes, so that's confusing me as well. Does the rating have anything to do with burnin testing?

-Peter

[trevorus]

Re: Tube rating question

It's to do with the point they start to breakup. Or clean headroom. It also makes it easier on fixed bias amps to drop in tubes without a rebias.

[ACH91332]

Re: Tube rating question

If I were you I would buy from an actual tube seller like tubedepot.com or thetubestore.com.

I just wouldn't trust Musicians Friend or Guitar Center for that stuff. Plus the two tube places I mentioned give you info on the tubes and also mark the tubes with test points as well.

[trevorus]

Re: Tube rating question

If I were you I would buy from an actual tube seller like tubedepot.com or thetubestore.com.

I just wouldn't trust Musicians Friend or Guitar Center for that stuff. Plus the two tube places I mentioned give you info on the tubes and also mark the tubes with test points as well.

Agreed 120%. They are the only two tube retailers I have dealt with, and they never leave me wanting.

[FuseG4]

Re: Tube rating question

I mostly get vintage tubes off ebay but if I'm buying new production tubes (like if I'm out of $$$) then yeah thetubestore.com and tubedepot.com.

[guitfiddle]

Re: Tube rating question

Back in the day, tubes that would now be a 2 or 3 on the scale would have been chucked into the trash bin, as would have the ones over 7 or 8. Those are out of line with the original design specs.

To find the ones that are right down the middle, I'd find either some good used ones from way back, NOS, or new production that rides the 5 or 6 rating...they'll be closest to the tube's specs.

There is a bit of a problem with using tubes at "lower rating" numbers. After 1/2 a dozen years at Groove Tube it became very clear to me that tubes with high or low numbers are tubes that are not close to design spec, as in, something is "wrong" with the tubes basically. These high and low rating numbers are tubes that have problems in assembly, improper workmanship, low emissions or other problems. In the end the high rating tubes will generally fail earlier than expected and the lower rating tubes will not sound proper or at times develop full output. I proved these things to myself and others countless times in my role as tech support for GT and was the only one on site at GT that could program the tube testing machines.